Engine - Poor Cold Driveaway: Overview

TS83-062

March 23, 1983
Engine Fuel
1982-1983 SENTRA MPG

E ENGINE COLD DRIVEAWAY COUNTERMEASURE


This bulletin describes additional cold driveaway countermeasures that may be applied to 1982 and 1983 Sentra MPG vehicles. These countermeasure consists of modifications to the choke heater, carburetor, and spark timing control system, and replacement of the exhaust manifold cover, and includes adjustment to idle mixture and spark plug replacement, if necessary.

This bulletin also summarizes service procedures and parts and warranty information from previous MPG cold driveaway countermeasure technical bulletins.

All applicable countermeasures must be applied to the vehicle to maximize cold start and driveaway performance. To determine the applicable countermeasures, service procedures, and parts information for an incident vehicle, refer to Chart 1.




CHART 1 - COLD DRIVEAWAY COUNTERMEASURE APPLICATION

If Chart 1 indicates that choke chamber and carburetor insulator should be applied, proceed with Step 1. If not, go to Procedure 2, air bleeds, throttle chamber, page 5.
Service Procedures
1. Choke chamber, carburetor insulator



1. Remove air cleaner.

2. Disconnect fuel hose, vacuum hoses, throttle cable, and carburetor wiring harness, and remove the carburetor assembly.

3. Disconnnect vacuum hoses A and B from the choke chamber.



4. Disconnect choke connecting rod from choke chamber.

5. Remove choke chamber screws D (See Figure 2). Remove choke heater wire from carburetor electrical connector by depressing locking tabs on terminal.
6. With choke chamber loose, remove accelerator pump rod from throttle lever. Remove choke chamber.

7. With compressed air, blow passages, castings, and parts until they are dry.
II. Air Bleeds,Throttle Chamber



If Chart 1 indicates that air bleeds and throttle chamber are required, proceed with Step 10. If not, go to Procedure 3, Distributor Vacuum Controller, page 13.

8. Remove air cleaner, if not already removed.

9. Disconnect fuel hoses, vacuum hoses, throttle cable, carburetor wiring harness and remove carburetor assembly, if not already removed.

10. Disconnect throttle chamber fixing screw.
11. Remove vacuum break hose from choke chamber (See Figure 1), if not already removed.



12. Remove throttle opener servo diaphram (with bracket) if not already removed.



13. Disconnect choke chamber fixing screws (five), if not already removed.



14. Remove choke chamber assy. Be careful not to drop the carburetor inner parts.



15. Replace primary slow air bleed.



16. Replace primary main air bleed.



17. Disconnect throttle chamber fixing screws (two) and return spring.



18. Remove and replace throttle chamber assy.

19. Installation is in reverse order of removal.

NOTE: Apply silicone grease to air fuel ratio solenoid O-ring.



20. Remove float from the former choke chamber and install it on the new choke chamber. Check float level adjustment as follows:

A. Turn down choke chamber to allow float to come into contact with needle valve, and measure "H", (Figure 3).
When "H" is approximately 0.47., the top float position is correct. It can be adjusted by bending the float seat. Upon completion of the adjustment, check fuel level with attached level gauge.

B. Adjust bottom float position so that clearance "h" between float seat and needle valve stem is 0.051 to 0.067 in., when float is fully raised. Bend float stopper as required.

C. After adjustments in steps A and B, make sure that when fuel is delivered to the float chamber, the fuel level is maintained at fuel level mark.



21. Throttle open adjustment

Set the following specification by adjusting screw.



22. Fast idle cam adjustment.

A. Disconnect the vacuum hose from the vacuum break diaphragm.
B. Push the vacuum break stem in, as shown, and install a blind plug to hold the vacuum break stem in this position, C. Turn the throttle lever to the wide open position, then release.

D. Adjust clearance "A": between primary throttle valve and inner carburetor wall by turning fast idle adjusting screw.



(see illustration).

Clearance "A":

M/T 0.08+/-0.07mm

(0.0315 + 0.0028 in.)

A/T 1.07+/-0.07mm

(0.0421 + 0.0028 in.)
Figure 14
E. Remove blind plug and reinstall the vacuum hose removed in Step A.

23. Install choke heater wire in the carburetor electrical connector.

24. If applicable, remove old carburetor insulator and install countermeasure insulator.

25. Install carburetor and connect fuel hoses, vacuum hoses, throttle cable, and carburetor wiring harness.